JPH08160716A - Electrifying member - Google Patents

Abstract

PURPOSE: To improve such problems as melt sticking or deposition of a toner caused during long-term use, problems of contamination of a photosensitive body or problems of adhesion of a photosensitive body. CONSTITUTION: This electrifying member is used to charge a body to be charged by bringing this member into contact with the body to be charged and applying voltage between this member and the body to be charged. At least the surface layer of the electrifying member contains a polyurethane as a structural material obtd. by using polyolefin polyol, polyoxytetramethylene polyol or a mixture of these as a polyol and liquid diphenylmethane-4,4'-diisocyanate as an isocyanate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charged body such as a photoconductor used in an electrostatic latent image process in a copying machine, a printer or the like, and more particularly to a charging body used for charging the charged body. It relates to members.

[0002]

2. Description of the Related Art Conventionally, in an electrostatic latent image process of a copying machine, a printer or the like, the surface of a developing area of a photoconductor is first charged to a uniform potential by an appropriate high voltage charging means, and then the charged area of the photoconductor is charged. Image light from an optical system is projected, and the potential of the portion where the light is incident changes to form an electrostatic latent image. Further, a method of printing is adopted by attaching toner to the latent image area and transferring the toner image onto a sheet.

In this case, the corona discharge method has been generally adopted as the method of initially charging the photosensitive member. However, this corona discharge method requires application of a high voltage of 5 to 10 KV, which is not preferable from the viewpoint of safe maintenance of the machine. Furthermore, since the harmful substances occurs, such as ozone and NO _x during the corona discharge, there are also environmental issues.

Therefore, as described in Japanese Patent Application Laid-Open Nos. 1-20518 and 1-211779,
That is, there has been proposed a method of charging a charged body by bringing a charging member to which a voltage is applied into contact with a charged body such as a photoconductor. According to such a charging contact method, charging can be carried out at a lower applied voltage than that of the corona discharge method, less ozone is generated, and various problems associated with the conventional corona discharge method can be solved. effective.

[0005]

However, recently, in the above-mentioned contact charging method, when a conductive rubber roller having a coating layer, for example, is used, there is no problem at the beginning of use, but a cleaning blade is used for a long period of time. The toner that has slipped through the layer is laminated and fixed on the conductive rubber roller,
It has become clear that image abnormalities such as fogging occur, or that toner sticks to the photoconductor and causes toner fusion, which similarly causes new problems such as image abnormalities.

With respect to this problem, it is possible to obtain the effect of reducing the hardness of the roller as much as possible. However, in order to reduce the hardness, it is necessary to use a soft material,
As such a material, for example, a plasticizer may be used. However, when the plasticizer is used, it migrates to the photoconductor and is contaminated, or the adhesive force of the plasticizer causes the charging member and the photoconductor to be stored during long-term storage. Will cause problems such as close contact.

In view of the above-mentioned circumstances, the present invention provides a charging member which solves and improves various problems such as toner fusion, toner accumulation, and other problems during durability, photoconductor contamination, and photoconductor adhesion. That is the purpose.

[0008]

That is, the invention according to claim 1 charges the charged body by bringing the charged body into contact with the charged body and applying a voltage between the charged body and the charged body. At least the surface layer of the charging member to use a polyolefin polyol or polyoxydetramethylene polyol or a mixture thereof as a polyol,
Liquid diphenylmethane-4 as isocyanate,
It contains a polyurethane obtained by using 4'-diisocyanate as a constituent material.

Further, the invention according to claim 2 is that, as the isocyanate, uretonimine-modified diphenylmethane-4,4'-diisocyanate or carbodiimide-modified diphenylmethane-4,4'-diisocyanate or phase-produced diphenylmethane-4,4'-diisocyanate is used. Alternatively, it includes a mixture thereof.

The invention according to claim 3 is one in which carbon black is added to polyurethane.

In the invention according to claim 4, the volume resistivity of the polyurethane is 10 ^{4 to} 10 ¹¹ Ω · cm.

Further, in the invention according to claim 5, the surface has a micro hardness of 65 degrees or less.

Further, according to the invention of claim 6, the surface roughness of the surface layer is 30 μm or less in 10-point average roughness.

[0014]

In the present invention, at least the surface layer of the charging member for charging the member to be charged by contacting the member to be charged and applying a voltage between the member and the member to be charged is a polyolefin polyolefin. Alternatively, by using polyoxytetradimethylene polyol or a mixture thereof and using polyurethane obtained by using liquid diphenylmethane-4,4′-diisocyanate as an isocyanate as a constituent material, toner fusion,
It is possible to simultaneously solve problems such as toner accumulation at the time of endurance, photoconductor contamination problem, and photoconductor adhesion problem.

[0015]

Embodiments of the present invention will be described in detail below. Since the charging member of the present invention is of the contact charging type, it is not particularly limited to the shape as long as it comes into contact with the body to be charged, but various types such as roll-shaped, plate-shaped, block-shaped, and spherical shapes can be used. The shape is applicable, but the shape of roll or plate is usually preferable.

In the present invention, at least the surface layer of these charging members uses polyolefin polyol or polyoxytetramethylene polyol or a mixture thereof as the polyol, and as the isocyanate, uretonimine-modified diphenylmethane-4,4'-diisocyanate, liquid diphenylmethane. The polyurethane obtained by using -4,4'-diisocyanate is used as a constituent material.

Examples of the polyolefin polyol include polybutadiene polyol, polyisoprene polyol and hydrogenated products thereof. As the isocyanate, liquid diphenylmethane-4,4 '
-Diisocyanate can be mentioned, among which uretonimine-modified diphenylmethane-4,4'-diisocyanate or carbodiimide-modified diphenylmethane-4,4'-diisocyanate or crude diphenylmethane-4,4'-diisocyanate (crude MD
It is preferable to use I), or a mixture thereof.

The amount ratio of polyol and isocyanate is
It is suitable to adjust the ratio of isocyanate groups to hydroxyl groups in the polyol to be 0.7 to 2.0, preferably 0.8 to 1.3. Below this range, contamination of the photoconductor may occur, and above this range, the polyurethane becomes hard.

Isocyanates have a functional number of 2.0 to 5.
It is suitable to use 0, preferably 2.5 to 4.0. Below this range, contamination of the photoconductor may occur, and above this range, polyurethane may become brittle.

Carbon black is added to the urethane as needed. The type of carbon black is not particularly limited, and examples thereof include furnace type, channel type, thermal type, and surface-treated carbon mainly for paints and inks. The amount of carbon black is also not particularly limited, but usually about 0.05 PHR to 50 PHR is often used with respect to the polyol.

Polyurethane may be produced by any method, for example, a method of blending carbon black into a polyurethane prepolymer and crosslinking and curing the prepolymer, or blending carbon with a polyol and subjecting this polyol to a one-shot method. It is manufactured by a method such as a method of reacting with polyisocyanate, a method of diluting with a solvent to obtain a paint state, and then curing.

Further, at this time, it may be foamed as required to produce a foam body. Anyway, the above-mentioned urethane should just be contained as a constituent material of at least the surface area of the charging member. For example, as the roll shape, the conductive roll illustrated in FIGS.

FIG. 1 shows the urethane layer 2 of the present invention provided on the outer circumference of a shaft 1 made of a highly conductive material such as stainless steel, plated iron, brass and conductive plastic.

FIG. 2 shows, for example, butadiene rubber, on the outer periphery of the shaft 1 made of a highly conductive material such as stainless steel, plated iron, brass and conductive plastic.
A conductive elastic layer 3 made of chloroprene rubber, silicone rubber, urethane rubber or the like is provided, and the polyurethane layer 2 of the present invention is further provided on the layer. in this case,
The polyurethane layer 2 is appropriately selected and formed by an ordinary casting method or a dip coating method.

The volume resistivity of the polyurethane of the present invention is preferably adjusted to 10 ⁴ to 10 ¹¹ Ω · cm.
Below this range, leaks are likely to occur, and above this range, fog is likely to occur. The microhardness of the surface layer containing the polyurethane of the present invention is suitably 65 degrees or less, preferably 60 degrees, more preferably 55 degrees or less. The surface roughness of the surface layer containing the polyurethane of the present invention is preferably 30 μm or less in terms of 10-point average roughness.

Therefore, by using the charging member of this embodiment, problems such as toner fusion, toner accumulation and the like at the time of endurance, photoconductor contamination problem, and photoconductor adhesion problem can be improved.

Next, the present invention will be specifically described by showing Examples and Comparative Examples according to the present invention, but the present invention is not limited to the following.

Example 1 300 g of polyisoprene polyol having a molecular weight of 2800 was mixed with 60 g of FT carbon and stirred for 60 minutes. After that, the crude MDI is set to 38.
5 g was added and stirred for 3 minutes. Next, this reaction mixture was poured into a mold in which a shaft was placed, and a curing reaction was performed at 90 ° C. for 10 hours to prepare a roller. The roller had a micro hardness of 49 degrees and a surface roughness of 6 μm.

[Example 2] Polyisoprene polyol 2
00 g, toluene 100 g, methyl ethyl ketone 100
After adding 500 g of glass beads to 42 g of FT carbon and dispersing with red devil for 10 hours, 25.7 g of crude MDI was further added and dispersed for 5 minutes to prepare a paint. A roll having a polybutadiene rubber layer having 18 parts of carbon added on the shaft was dipped in the above coating material to form a roll having a 100 μm thick urethane layer formed on the outermost surface. This roller had a micro hardness of 52 degrees and a surface roughness of 5 μm.

Comparative Example 1 300 g of a polyether polyol having a molecular weight of 5000 was mixed with 60 g of FT carbon and stirred for 60 minutes. After that, the crude MDI 2
7.9 g was added and stirred for 3 minutes. Next, the reaction mixture is poured into a mold in which a shaft is arranged, and the mixture is allowed to stand at 90 ° C. for 1 hour.
A curing reaction was performed for 0 hours to prepare a roller. The roller had a micro hardness of 65 degrees and a surface roughness of 8 μm.

Comparative Example 2 60 g of FT carbon was mixed with 300 g of a polyether polyol having a molecular weight of 5000 and stirred for 60 minutes. After that, 18.3 g of TDI was added and stirred for 3 minutes. Next, this reaction mixture was poured into a mold in which a shaft was placed, and a curing reaction was performed at 90 ° C. for 10 hours to prepare a roller. The roller had a micro hardness of 70 degrees and a surface roughness of 7 μm.

Comparative Example 3 300 g of polyisoprene polyol having a molecular weight of 2800 was mixed with 60 g of FT carbon and stirred for 60 minutes. Then add 23.7 TDI,
Stir for 3 minutes. Next, this reaction mixture was poured into a mold in which a shaft was placed, and a curing reaction was performed at 90 ° C. for 10 hours to prepare a roller. The roller had a micro hardness of 59 degrees and a surface roughness of 8 μm.

Comparative Example 4 A roller similar to that of Example 1 was prepared except that the surface roughness was 35 μm. As described above, the following items were tested for each roller produced in each of the above-mentioned Examples and Comparative Examples.

(1) Toner fusion bonding Each roller is incorporated into a laser printer, and continuous 800
The image is printed out. After printing 8000 sheets, a black image is displayed and the number of white spot-like abnormalities in the black image is evaluated.

(2) Toner accumulation After printing the above 8000 sheets, images are printed in an environment of 15 ° C. and 10% RH, and it is determined whether or not there is any abnormality such as sand.

(3) Contamination of the photoconductor With the roller and the photoconductor drum in contact with each other, 40 ° C. 95
After left in a% RH environment for 1 month, images are displayed at room temperature to evaluate whether there is an image abnormality due to contamination.

(4) Adhesion of Photoreceptor After leaving the roller and the photoconductor drum in contact with each other for 3 days in an environment of 60 ° C., it is evaluated whether or not the roller and the photoconductor drum are in contact with each other. Table 1 below shows the knowledge obtained from the comparison of each roller between the example and the comparative example.

[0038]

[Table 1]

[0039]

As described above, according to the charging member of the present invention, at least the surface layer of the charging member,
Polyolefin polyol or polyoxytetramethylene polyol or a mixture thereof is used as the polyol, and polyurethane obtained by using liquid diphenylmethane-4,4'-diisocyanate as the isocyanate is contained as a constituent material, and it is brought into contact with a body to be charged, Even if a voltage is applied between the contacted member and the charged member, the occurrence of phenomena such as toner fusion and toner accumulation on the charged member can be effectively suppressed, and when the charged member is not used for a long period of time. It is possible to adhere to the body to be charged and prevent contamination. Therefore, according to the present invention, the problem of durability and the problem of photoreceptor contamination,
Further, it becomes possible to provide a high-quality charging member for electrostatic latent image formation of the contact charging system, such that the problem of adhesion to the photoreceptor can be solved at the same time.

[Brief description of drawings]

FIG. 1 is a sectional view showing a charging member according to the present invention.

FIG. 2 is a cross-sectional view showing another charging member according to the present invention.

[Explanation of symbols]

 1 shaft 2 urethane layer 3 elastic layer

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[Procedure amendment]

[Submission date] January 24, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 2

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

[0009] The invention described in claim 2, as an isocyanate, uretonimine modified diphenylmethane-4,4'-diisocyanate or carbodiimide-modified diphenylmethane-4,4'-diisocyanate or crude steel diphenylmethane-4,4'-diisocyanate Alternatively, it includes a mixture thereof.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0034

[Correction method] Change

[Correction content]

(1) Toner fusion bonding Each roller is incorporated into a laser printer, and continuous 800
0 images are printed. After printing 8000 sheets, a black image is displayed and the number of white spot-like abnormalities in the black image is evaluated.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Yasushi Inoue 3-5-5-656 Ogawa Higashi-cho, Kodaira-shi, Tokyo (72) Inventor Takahiro Kawagoe 1302-57 Aobadai, Tokorozawa, Saitama

Claims (6)

[Claims] 1. A charging member for charging a charged body by bringing the charged body into contact with the charged body and applying a voltage between the charged body and the charged body, the surface area of which is at least a polyolefin polyol. Alternatively, a charging member comprising a polyurethane obtained by using polyoxydetramethylene polyol or a mixture thereof and liquid diphenylmethane-4,4'-diisocyanate as an isocyanate as a constituent material. 2. As the isocyanate, uretonimine-modified diphenylmethane-4,4'-diisocyanate or carbodiimide-modified diphenylmethane-4,4'-
Diisocyanate or phase-produced diphenylmethane-4,
The charging member according to claim 1, which contains 4'-diisocyanate or a mixture thereof. 3. A charging member according to claim 1, wherein carbon black is added to polyurethane. 4. A volume resistivity of polyurethane 10 ⁴ to 1
The charging member according to claim 1, wherein the charging member has a resistance of 0 ¹¹ Ω · cm. 5. The charging member according to claim 1, wherein the surface has a micro hardness of 65 degrees or less. 6. The surface roughness of the surface layer is 3 at 10 point average roughness.
The charging member according to claim 1, wherein the charging member has a thickness of 0 μm or less.